This application requests support for a FASEB Summer Conference entitled Gastrointestinal Tract XIII: Molecular and Cell Biology of Development, Physiology, Inflammation, and Host defense of the Gastrointestinal tract (Drs. S. Sitaraman, C, Tayor, and W. Lencer co-chairs). The 5 day conference will be the 13th in a series of biennial meetings that over the last 24 years has provided an intense and intimate venue for presentation, discussion, and exchange of ideas among scientists at the forefront of research in fields related to gastrointestinal health and disease. It also provides a venue for young scientists and post-doctoral fellows to meet, live, and work together with established investigators in the field. The topic of the 2009 program is on how the diverse cell types in the intestinal mucosa define the epithelial barrier, how they relate to the prokaryotic microbiome of the intestinal lumen, and how they relate to each other structurally and functionally. The conference will be held from August 9-14, 2009 in Snowmass Colorado. The Snowmass Conference Center is a well-established site for FASEB conferences and is fully equipped and well suited to support this meeting. Thirty-seven speakers and session chairs are confirmed. Three poster sessions are planned and an afternoon will be devoted to a Career Development Workshop for young investigators lead by senior officials from the NIH and CCFA.